Motor

Abstract

Motor having small torque ripple. In a core of an armature of a motor, teeth are disposed radially around a center axis, arrangement of pitch angles of the teeth having different picth angles, or arrangement of tip end widths of the teeth having different tip end widths is repeated three or more times in the circumferential direction, the number of teeth is greater than the number of poles of the field magnet and with this structure, the tip ends of the teeth are varied, and with this effect also, the torque ripple is reduced.

1 . An electric motor comprising: 
 a stator having an armature;    a rotor having a field magnet for generating a torque around a center axis between the armature and the rotor; and    a bearing mechanism for supporting the rotor around the center axis such that the rotor can rotate relative to the stator; wherein    a plurality of teeth of a core of the armature are disposed radially around the center axis, a gap is formed between inner tops of adjacent teeth and a pitch angle of the gap is defined around the center axis, a pitch angle arrangement set which has at least two different pitch angles formed between the adjacent teeth is defined, the pitch angle arrangement set is repeated three or more times in the circumferential direction around the center axis, and    a number of teeth is greater than a number of magnetic poles of the field magnet.    
   
   
       2 . The motor according to  claim 1 , wherein the motor is driven by a rectangular wave energization method.  
   
   
       3 . The motor according to  claim 2 , wherein the motor is a driving source for assisting a driving operation of a vehicle.  
   
   
       4 . The motor according to  claim 1 , wherein the core is formed by laminating thin steel sheets while rotating a direction of the sheets in accordance with a repetition of the pitch angle arrangement set.  
   
   
       5 . The motor according to  claim 4 , wherein the motor is a driving source for assisting a driving operation of a vehicle.  
   
   
       6 . The motor according to  claim 1 , wherein a number of repetitions of the pitch angle arrangement set is not a multiple of a number of the magnetic poles of the field magnet.  
   
   
       7 . An electric motor comprising: 
 a stator having an armature;    a rotor having a field magnet for generating a torque around a center axis between the armature and the rotor; and    a bearing mechanism for supporting the rotor around the center axis such that the rotor can rotate relative to the stator; wherein 
 a plurality of teeth of a core of the armature are disposed radially around the center axis, a gap is formed between inner tops of adjacent teeth and a pitch angle of the gap is defined around the center axis, a pitch angle arrangement set which has at least two different pitch angles formed between the adjacent teeth is defined, the pitch angle arrangement set is repeated three or more times in the circumferential direction around the center axis,  
 a number of teeth is greater than a number of magnetic poles of the field magnet, and  
 a tip end width is formed at inner top of tooth, an angle of a tip end width of tooth is defined around the center axis, a tip end width arrangement set which has at least two different tip end widths of the teeth is defined, the tip end width arrangement set is repeated in accordance with the repetition of the pitch angle arrangement set arranged regularly in the circumferential direction around the center axis.  
   
   
   
       8 . The motor according to  claim 7 , wherein twelve teeth are arranged around the center axis, a total angle of the pitch angle arrangement set is 120°, the field magnet has four poles in the circumferential direction around the center axis.  
   
   
       9 . The motor according to  claim 8 , wherein the motor is driven by a rectangular wave energization method.  
   
   
       10 . The motor according to  claim 9 , wherein the core is formed by laminating thin steel sheets while rotating a direction of the sheets in accordance with the repetition of the pitch angle arrangement set.  
   
   
       11 . The motor according to  claim 10 , wherein: 
 tip ends of the teeth are directed to the center axis; and    the field magnet is opposed to inner peripheral surfaces of the teeth.    
   
   
       12 . The motor according to  claim 11 , wherein any two or more magnetic pole boundaries of the field magnet do not match with the slot between the teeth at the same time in any of cross section intersecting the center axis at right angles.  
   
   
       13 . The motor according to  claim 12 , wherein in the teeth disposed radially, tip end widths of any of the adjacent teeth are different from each other.  
   
   
       14 . The motor according to  claim 13 , further comprising a plurality of coils wound in a distributed manner; wherein: 
 each coil extends through three teeth comprising a tooth having narrowest width of the teeth among the three teeth interposed between the other two teeth; and    the coils are disposed a same number each on each of inner and outer peripheral sides of the teeth.    
   
   
       15 . The motor according to  claim 14 , wherein the motor is a drive source which assists driving operation of a vehicle.  
   
   
       16 . The motor according to  claim 15 , wherein the motor directly assists a power steering system of an automobile.  
   
   
       17 . An electric motor comprising: 
 a stator having an armature;    a rotor having a field magnet for generating a torque around a center axis between the armature and the rotor; and    a bearing mechanism for supporting the rotor around the center axis such that the rotor can rotate relative to the stator; wherein    the field magnet has four poles in a circumferential direction around the center axis, a plurality of teeth of a core of the armature are disposed radially around the center axis, a gap is formed between inner tops of adjacent teeth and a pitch angle of the gap is defined around the center axis, a pitch angle arrangement set which has at least two different pitch angles formed between the adjacent teeth is defined, the pitch angle arrangement set is repeated three or more times in the circumferential direction around the center axis,    a tip end width is formed at inner top of tooth, an angle of a tip end width of tooth is defined around the center axis, a tip end width arrangement set which has at least two different tip end widths of the teeth is defined, the tip end width arrangement set is repeated in accordance with the repetition of the pitch angle arrangement set arranged regularly in the circumferential direction around the center axis, a slot gap is formed between the tip ends of adjacent teeth and a slot angle of the slot gap is defined around the center axis,    a core of the armature comprises a total twelve teeth in which an arrangement set defined using three kinds of teeth a, b and c which are combinations of sizes of θw 1  and W 1 , θw 2  and W 2 , and θw 3  and W 3  which are angles of tip end widths around the center axis and width of thinnest portion of the teeth is repeated three times in the circumferential direction in a radially inward around the center axis,    the angles of tip end widths are in a relation of θw 1 >θw 2 >θw 3 , and the thinnest widths are in a relation of W 1 >W 2 >W 3 ,    the arrangement is four of teeth in an order of a, b, a, c,    a pitch angle θ 1  between the teeth a and b indicated with angle around the center axis, a pitch angle θ 2  between the teeth a and c, a slot angle θ between the teeth tip ends, and the tip end width angles of the teeth are in a relation of    θ 1 =30°+α, θ 2 =30°−α, θw 3 >>α>0°, 2α>θ≧0°, 2θw 3 >θw 1 , 40°−(4/3)(α+θ)>θw 1 >30°, 30°−2(α+θ)>θw 3 >20°−(2/3)(α+θ), θw 2 =θw 3 +4α   (preferable α is about 1°),    the motor further comprises total six coils wound in a distributed manner, the six coils are disposed such that three of them is disposed on each of inner and outer peripheral sides of the teeth, each coil extends through three teeth comprising the teeth a and the tooth b or c interposed between the teeth a, and    the motor is driven by energizing the coil with rectangular current.    
   
   
       18 . The motor according to  claim 17 , wherein the core is formed by laminating thin steel sheets while rotating a direction of the sheets in accordance with a repetition of the pitch angle arrangement set.  
   
   
       19 . The motor according to  claim 18 , wherein a polarized phase of the field magnet or disposition phase of the teeth has a skew structure which is gradually varied depending upon position in the center axis direction.  
   
   
       20 . The motor according to  claim 19 , wherein the motor directly assist a power steering system of an automobile.